#include <bits/stdc++.h>

using namespace std;
int ch[26] = {0};
char output[200010] = {0};
void solve(void)
{
    memset(ch,0,sizeof(ch));
    int n;
    int zeroNum = 0;
    cin >> n;
    int tmp = 0;
    int index = 0;
    for (int i = 0; i < n; i++)
    {
        scanf("%d", &tmp);
        if (tmp == 0)
        {
            ch[zeroNum]++;
            output[index++] = 'a' + zeroNum;
            zeroNum++;
        }
        else
        {
            for (int j = 0; j < zeroNum; j++)
            {
                if (ch[j] == tmp )
                {
                    output[index++] = 'a' + j;
                    ch[j]++;
                    break;
                }
            }
        }
    }
    output[index] = '\0';
    printf("%s\n",output);
}
int main(void)
{
    int n;
    cin >> n;
    while (n-- > 0)
    {
        solve();
    }
}
